GIA stands for Gemological Institute of America, or Gemological Institute of America. It is a non-profit organization for the identification and research of jewelry donated by members of the jewelry industry. The GIA certificate issued by gia carries out a comprehensive assessment of the diamond's weight, color, clarity, cut, etc., that is, the 4C information, so as to determine the quality of a diamond. GIA is the authority on the diamond grading system and is the agency that certifies the quality of diamonds.